1. Field of the Invention
The present invention relates generally to a tower type multi-color printing press, in which a plurality of printing sections are stacked vertically and a paper web is passed through the printing sections in sequential order to print images on the paper web by the respective printing sections. More specifically, the invention relates to a tower type multi-color printing press having heating means for heating a printed image.
2. Description of the Related Art
A tower type multi-color printing press having means for drying a printed paper has been disclosed in Japanese Unexamined Patent Publication Nos. Heisei 7-285213, 8-66997 and 8-230138, for example.
Each the tower type multi-color printing press disclosed in these publications is provided with heating means or heating means and cooling means at a downstream position passed through all printing sections in a direction of feeding a paper web for drying a printed image after completion of printing by the respective printing sections.
The heating means is not clearly disclosed in Japanese Unexamined Patent Publication Nos. 7-285213 and 8-230138. However, if there are no indication of a special printing, such as printing using a UV ink and if no particular drying function is not clearly disclosed, it is typical to interpret that an apparatus disclosed as drying means for these publications is a heating means.
On the other hand, as a drying function of the ink printed on a paper surface, in addition to a drying function for evaporating a solvent by heating the ink and solidifying a thermoplastic material contained in the ink by cooling the ink, there is another well known drying function by penetrating a liquid component of the ink having high flowability in a paper fiber to leave solid component on the paper surface.
In the inventions disclosed in the foregoing publications, it is required to evaporate the solvent from a printed image after completion of printing by the respective printing sections, namely, in a relative thick ink layer, in which a plurality of inks are overlaid. Accordingly, it is required to elevate the entire thick ink layer in a short period. Also, in order to sufficiently evaporate the solvent from the entire thick ink layer, it is required to maintain high temperature for a relatively long period. Accordingly, a large heat amount is necessary. Also, in order to maintain high temperature over a relatively long period, the heating means inherently becomes quite bulky to the extent to be larger than a printing unit in the respective printing sections to require quite a large installation space. Furthermore, a mechanism inherently becomes quite complicated.
On the other hand, as heating means, a production cost becomes significantly large and inspection and maintenance require substantial period. Furthermore, due to complexity of the mechanism, and the possibility of occurrence of failure becomes relatively high.